High sensitivity thermomagnetic circuit breaker



Nov. 10, 1964 w. H. VOGELSBERG 3,156,796

HIGH SENSITIVITY THERMOMAGNETIC CIRCUIT BREAKER Filed July 31, 1961 4 Sheets-Sheet l I car-Z- pie/OZ 19,27

1964 w. H. VOGELSBERG 3,156,796

HIGH SENSITIVITY THERMOMAGNETIC CIRCUIT BREAKER Filed July 31, 1961 4 Sheets-Sheet 2 INVENTOR. 14/4; 752 M mezuazm Nov. 10, 1964 W. VOGELSBERG HIGH SENSITIVITY THERMOMAGNETIC CIRCUIT BREAKER Filed July 51, 1961 4 Sheets-Sheet 3 INVEN TOR. W41 75/? b. IdZZJJA-K Array/v5 W Nov. 10, 1964 w. H. VOGELSBERG 3,156,796

HIGH SENSITIVITY THERMOMAGNETIC CIRCUIT BREAKER INVENTOR.

United States Patent 3,156,796 HIGH SENSITIVITY THERMGMAGNETIC CIRCUIT BREAKER Walter H. Vogelsberg, Narbeth, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed July 31, 1961, Ser. No. 128,071 6 Claims. (Cl. 200-88) This invention relates to automatic circuit breakers in general and more particularly to an improved magnetic instantaneous trip means structure.

Automatic circuit breakers are usually provided with instantaneous trip means comprising a magnetic structure which, when subjected to an overload current, actuates a mechanism to release a latch mechanism maintaining the circuit breaker contacts in engagement. As a circuit breaker rating increases more powerful operating springs are used so that the forces required for unlatching also increases.

In an armature magnet of the conventional type the force of attraction between the armature and magnet is inversely proportional to the square of the air gap when saturation elfects are ignored. If the armature is pivotally mounted the torque produced to overcome the latching forces is directly proportional to the distance from the armature pivot to the armature itself.

Thus, by mounting the armature structure closer to its pivot the air gap is decreased and the force of attraction is increased in a squared relationship, while the torque developed decreases as the first power. It follows that there is a linear gain in efiiciency and the most powerful magnet design possible is one which includes a zero air gap at the pivot. Except for saturation effects the force developed reaches extremely high values.

Accordingly, a primary object of this invention is to provide a novel construction for the automatic trip means of a circuit breaker.

Another object is to provide a circuit breaker magnetic trip means in which the current passing through a single turn energizing conductor is eifective to overcome high latching forces.

Still another object is to provide a circuit breaker automatic magnetic trip means in which the armature is pivoted at a point located substantially at the ends of the pole faces.

A still further object is to provide a circuit breaker magnetic trip means in which the armature is pivoted directly to the magnetic with the pivot point extending across pole faces of opposite polarities.

These as well as other objects of this invention shall become readily apparent after reading the following description of the accompanying drawings in which:

FIGURE 1 is a fragmentary view of a circuit breaker illustrating a typical prior art arrangement for a circuit breaker automatic tripping means.

FIGURE 2 is a side elevation of a circuit breaker automatic tripping unit constructed in accordance with the teachings of the instant invention.

FIGURE 2A is a cross section taken through line 2A2A of FIGURE 2 looking in the direction of arrows 2A.

FIGURE 23 is a front elevation of the armature in the trip unit of FIGURE 2.

FIGURE 3 is a perspective of a multi-phase molded case circuit breaker embodying the teachings of the in stant invention. In this view the circuit breaker cover has been removed to reveal the operating mechanism of the circuit breaker.

FIGURE 3A is a cross section taken through line 3A3A of FIGURE 3 looking in the direction of arrows ice FIGURE 4 is an exploded perspective of the magnetic trip device of the circuit breaker of FIGURE 3.

FIGURE 5 is a side elevation of the magnetic trip device of FIGURE 4.

FIGURE 6 is a rear elevation of the magnetic trip device of FIGURE 5 looking in the direction of arrows d6.

FIGURE 7 is a plan view of the magnetic trip device of FIGURES 5 and 6.

Now referring to the figures and more particularly to FIGURES 1 through 2B. Automatic trip device 200 of FIGURE 1 is typical of prior art devices including both magnetic and thermal tripping means. The magnetic or instantaneous tripping means comprises generally U- shaped magnet 201 and cooperating armature 202. Magnet 201 is fixedly mounted in the circuit breaker housing while armature 202 is mounted near one end 203 of elongated resilient member 204 whose other end 205 is fixedly secured to the circuit breaker housing. L-shaped latch member 206 for releasable cradle 207 is carried by spring member 204.

When armature 202 is attracted to magnet 201 spring member 204 is rotated counterclockwise about the stationary end 205 thereof. This moves latch member 206 to the right with respect to FIGURE 1 to unlatch the releasable cradle 207 and, as is Well known in the art, enables the main operating springs of the circuit breaker to disengage the contacts.

The thermal tripping means of unit 200 comprises elongated bimetallic element 210 having one end 211 fixedly secured to the circuit breaker housing. One end 212 of U-shaped member 213 is secured to the other end 214- of bimetal 210. The other end 215 of U-shaped member 213 is positioned so as to engage end 203 of spring member 204 upon deflection of bimetal 210 to the right with respect to FIGURE 1,

As is well known in the art, bimetal 210 passes between the legs of magnet 201 and forms the energizing turn thereof. When bimetal 210 is overheated, end 214 thereof moves to the right with respect to FIGURE 1. End 215 of member 213 engages spring member end 203 also moving it to the right with respect to FIGURE 1 to release cradle 207 from latch 206.

Fixed end 205 of spring member 204 forms a pivot for armature 201. The attracting force between magnet 201 and armature 202 must be sufiicient to develop a torque which will overcome the downward latching force transmitted through cradle 207 to latch 206 by the main operating spring of the circuit breaker.

In a device constructed in accordance with the instant invention, as illustrated in FIGURES 2-2E, automatic trip unit 300 includes instantaneous trip means comprising generally U-shaped magnet 301 and cooperating armature 302 while the thermal or time delay trip means comprises bimetallic element 303. One end 304 of bimetal 303 is fixedly mounted to the circuit breaker housing while the other end 305, upon heating of bimetal 303, is free to deflect to the right with respect to FIGURE 2. Latch member 3% for releasable cradle 307 is mounted to bimetal 303 near end 305 thereof by means of rivet 308 which also mounts transverse insulating member 309 of bimetal 303.

Armature 302 is a generally plate-like member having central cut-outs 311 and 312. Upper cut-out 311 provides clearance for spring member 313 which is secured at one end thereof by rivet 314 to armature 302. The other end of spring 313 abuts suitable formations of the circuit breaker housing biasing armature 302 to the position of FIGURE 2. The lower cut-out 312 provides clearance for bimetal 303.

Upper ears 315 of armature 302 provide locating shoulders 316 forming a pivot for armature 302 at the upper armature 2G2. faces 3191a, 3011b a-portion of the air gap is zero.

a edge ofmagnet 3M. Pivot 316 extends across oppositely polarized pole faces 301a, 3011; of magnet 3111 with spring 313 biasing armature 362 clockwise with respect to its pivot 316.

When .current of sutlicient magnitude flows through bimetal 303'sufiicient flux is generated by magnet 31to attract armature 3112. 'Lower ears 318 of armature 3132 pared to the moment arm between spring member end .1195 and latch 206.

FIGURES 3-7 illustrate a three-phase circuit breaker '10 whose magnetic trip means is constructed in accordance with the teachings of this invention. Circuit breaker ltlcomprises a molded housing having base'11 and removable cover 112. Base 11 is provided with longitudinal partitions 14, 15 which divide base 11 into three elongated compartments, one for each phase of circuit breaker'1t). Similar longitudinal partitions (not shown) areprovided for. cover 12.

The current path througheach phase of circuit breakerl'ti compriseslload terminal connector 16, load terminal strap, includingloop portion 18 having portion 21) of reduced cross sections which serves as a heater for bimetal trip element .21, connecting member 22, flexible member 23 to one end of movable contact arm 24. Movable contact 25 is mounted to the other end of contact arm 24 and is engageable with stationary contact 26 mounted to one end of line terminal strap 27 which is connected by screw means 29' to tulip connector 28 forming the lineterminal connection.

Trip free 'operatingmechanism '31? is provided to pivot movable tie bar 99 about pin 36. All three contact arms 24 arecarried by'tie bar 99 for simultaneously operating movable contacts 25 of all three phases into and out of engagement with theirassociatedstationary contacts '26. Operating mechanism 36 is of an overcenter toggle type well known to the art and is fully described in copending applicatiom'SerialNo. 108,812, filed May 9, 1961 entitled lJ-Shaped Cradle for Circuit Breaker, invented by Ernest R. Wortmann and assigned to the assignee of the .instant'invention. Handle 93 is provided for manual operation of mechanism 311 whiie overload device 97 isprovided for automatic tripping of mechanism 315.

Arc extinguishing means in the form of arc chute 411 is operatively positioned by suitable formations in base 11 to receive electric current arcs drawn between cooperating contacts 25, 26 upon separation thereof. 'Since the theory of arc interruption is well understood to'those skilled in the art elaboration of this point will not be undertaken at this time.

()verload device 97,'in addition to comprising a time delay tripping means comprising bimetal 21 also comprises instantaneous trip means 100. The latter com- .prises a generally U-shaped magnet. pole piece 1M. enerupper end thereof by means of slots 115, 116 of frame member 13%.

102 and bracket 114, respectively, which receive ears 117, 118 of bracket 114 and frame 192, respectively. Bracket 114 carries rotatable air gap adjusting member 121 which is received by aligned apertures 121, 122 in the arms of bracket 114. Fiber washer 123 is disposed adjacent to head 124 of member-12ti and is biased upward by compression spring 125 which rests against the upper arm of bracket 114. Washer 123 serves as a closure member for aperture 126 of cover '112 into which head 124 projects.

Member 120 includes longitudinal slot 127 which receives thebodyportion 128 of -member 131?. Members 120 and are secured to one another by means of roll pin 129 which extends through aligned apertures (not shown) in members 120 and 130. Compression spring 131, interposed between the lower arm of bracket 114 and seating portion 132 of member 130, biases member 130 hence member 120 upwardly. In the upward position, portion 133 of member 130 positioned at right angles to portion128 is in a plane with extensions 134- :136which project downward from the'top leg of bracket 114.. In this position one of the flat edge surfaces of portion 133 cooperates with oneof the extensions 134- 136 to maintain members 120-130 in a fixed angular position with respect to bracket 114. Members 121L130 may be rotated after depressing same until portion 1-33 is below the lower ends of extensions 134-136.

The elements of instantaneous trip device'ltm hereinbefore described are assembled as a unit prior to insertion and securement to base'11. Securement is accomplished by a single screw 138 which passes through frame aperture 139 and is received by a suitable threaded insert mounted to base-11. After the sub-assembly is mounted to base 11 current carrying loop 1-8-is-secured in place and'thereafter magnetic armature 140 is mounted to frame 1112.

Armature 14d comprises a plate-likemember whose lower end is provided with notch-141for the-passage of loop member18. Notch 141 is defined by projections whose lower ends are narrowed at 142, 1-43. The narrowed projection portions 142,.143are received by frame slots1 i4, 145, respectively, in the web offrame member 162. The cooperation ofprojection portions 142,143 and slots 144, 14 5 provides a pivotal connection between armature 14th and frame 102.

Tension spring 14-6 is secured-between armature ear 14? and frame ear 148 with these cars being operatively positioned so that the upper end of armature 140 is biased away from pole faces of pole piece 1% and the'lower end of 1413 is firmly seated'against the web of frameltiZ. It is to be noted that frame slots 144-, 145 are so positioned that even when armature14ti is not attracted to pole piece 1111, armature 141i rests against the lower end of the pole piece faces so thatno air gap exists at this pivot region which extends across the oppositely polarized pole faces.

The upper end of armature 14% includes extension 151 which carries adjusting screw 152 engageable with ear 153 of common trip bar 155. As is well known to the art, rotation of common trip bar 155 by the armature of the instantaneous trip device is effective to'bring about automatic tripping of the circuit breaker mechanism.

Armature 14 also carries another upwardly extending ear 156 which is engaged by downward extension 157 of member 1%. As member12t3 is rotated so too is This moves portion 157 thereof in relation to the plane of the-pole piecepole faces. The engagement between portions 157 and armature extension 1156 causes the size of the .V-shaped air gap 160 between armature 14d and the faces of pole piece1ti1' to change.

A fine adjustment, made atthe' factory, is achieved by bending extension-156 relative to the main portion of armature 1411 along line 161.

Thus, it is seenthat this invention provides a so-called Zero air gap at the pivot region between'a magnet and its cooperating armature whereby high unlatching forces are achieved with few magnet ener izing turns.

In the foregoing, the invention has been described only in connection with preferred embodiments thereof. Many variations and modifications of the principles of the invention within the scope of the description herein are obvious. Accordingly, it is to be bound not by the specific disclosure herein but only by the appending claims.

I claim:

1. A circuit breaker trip unit including an automatic magnetic tripping means comprising a nianget for generating flux in response to current flow through the circuit breaker, and an armature operatively positioned so that said flux passes therethrough; said magnet including a pair of pole faces lying in a plane; said armature being mounted for pivotal movement toward and away from said plane about an axis extending across edge surfaces of said pair of pole faces; bimetallic tripping means for deflection responsive to predetermined current flow in said circuit breaker; first means for mounting said magnetic tripping means, and second means for mounting said bimetallic tripping means; said first and second means being substantially independent, whereby a V-shaped air gap relationship of said armature and pair of pole faces is maintained independent of the deflection of said bimetallic tripping means thereto.

2. A circuit breaker trip unit including an automatic magnetic tripping means comprising a manget for generating flux in response to current flow through the circuit breaker, and an armature operatively positioned so that said flux passes therethrough; said magnet including a pair of polefaces lying in a plane; said armature being mounted for pivotal movement toward and away from said plane about an axis extending across edge surfaces of said pair of pole faces; 1 cans biasing said armature away from said plane whereby a generally V-shaped air gap is normally formed between said armature and said pole faces; bimetallic tripping means for deflection responsive to predetermined current flow in said circuit breaker; first means for mounting said magnetic tripping means, and second means for mounting said bimetallic tripping means; said first and second means being substantially independent, whereby the V-shaped air gap relationship of said armature and pair of pole faces is maintained independent of the deflection of said bimetallic tripping means.

3. A circuit breaker trip unit including an automatic magnetic tripping means comprising a manget for generating flux in response to current flow through the circuit breaker, and an armature operatively positioned so that said flux passes therethrough; said magnet including a pair of poles faces lying in a plane; said armature being mounted for pivotal movement toward and away from said plane about an axis extending across edge surfaces of said pair of pole faces; means biasing said armature away from said plane whereby a generally V-shaped air gap is normally formed between said armature and said pole faces; an operating mechanism latch means; said armature when moved toward said pole faces being effective to release said latch means bimetallic tripping means for deflection responsive to predetermined current flow in said circuit breaker; said bimetallic tripping means in operative engagement with said latch means for release of the latter as the bimetallic tripping means is deflected; first means for mounting said magnetic tripping means, and second means for mounting said bimetallic tripping means; said first and second means being substantially independent whereby the V-shaped air gap relationship of said armature and said pair of pole faces is maintained independent of the deflection of said bimetallic tripping means.

4. A circuit breaker trip unit including an automatic magnetic tripping means comprising a manget for gencrating flux in response to current flow through the circuit breaker, and an armature operatively positioned so that said flux pass-es therethrough; said magnet including a pair of pole faces lying in a plane; said armature being mounted for pivotal movement toward and away from said plane about an axis extending across edge surfaces of said pair of pole faces; means biasing said armature away from said plane whereby a generally V-shaped air gap is normally formed between said armature and said pole faces; said axis being operatively positioned so that one end of said gap is normally substantially zero; bimetallic tripping means for deflection responsive to predetermined current fiow in said circuit breaker; first means for mounting said mangetic tripping means, and second means for mounting said bimetallic tripping means; said first and second means being substantially independent, whereby the V-shaped air gap relationship of said armature and pair of pole faces is maintained independent of the deflection of said bimetallic tripping means.

5. A circuit breaker trip unit including an automatic magnetic tripping means comprising a magnet for generating flux in response to current flow through the circuit breaker, and an armature operatively positioned so that said flux passes therethrough; said magnet including a pair of pole faces lying in a plane; means normally maintaining one end of said armature in abutment with said magnet with generally V-shaped air gap between said armature said plane; said armature bein mounted for pivotal movement toward and away from said plane about an axis extending across edge surfaces of said pair of pole faces where said armature abuts said magnet; bimetallic tripping means for deflection responsive to predetermined current fiow in said circuit breaker; first means for mounting said magnetic tripping means, and second means for mounting said bimetallic tripping means; said first and second means being substantially independent, whereby the V-shaped air gap relationship of said armature and pair of pole faces is maintained independent of the deflection of said bimetallic tripping means.

6. A circuit breaker trip unit including an automatic magnetic tripping means comprising a manget for generating flux in response to current flow through the circuit breaker, and an armature operatively positioned so that said flux passes therethrough; said magnet including a pair of pole faces lying in a plane; means normally maintaining one end of said armature in abutment with an edge of said magnet lying in said plane; said edge forming a pivotal axis for said armature extending across edge surfaces of said pair of pole faces; said armature other end biased away from said plane and movable toward said plane when the magnitude of said flux exceeds a predetermined value; bimetallic tripping means for deflection responsive to predetermined current flow in said circuit breaker; first means for mounting said magnetic tripping means, and second means for mounting said bimetallic tripping means; said first and second means being substantially independent, whereby the relationship of said armature and pair of pole faces is maintained independent of the deflection of said bimetallic tripping means.

References Cited in the file of this patent UNITED STATES PATENTS 

1. A CIRCUIT BREAKER TRIP UNIT INCLUDING AN AUTOMATIC MAGNETIC TRIPPING MEANS COMPRISING A MANGET FOR GENERATING FLUX IN RESPONSE TO CURRENT FLOW THROUGH THE CIRCUIT BREAKER, AND AN ARMATURE OPERATIVELY POSITIONED SO THAT SAID FLUX PASSES THERETHROUGH; SAID MAGNET INCLUDING A PAIR OF POLE FACES LYING IN A PLANE; SAID ARMATURE BEING MOUNTED FOR PIVOTAL MOVEMENT TOWARD AND AWAY FROM SAID PLANE ABOUT AN AXIS EXTENDING ACROSS EDGE SURFACES OF SAID PAIR OF POLE FACES; BIMETALLIC TRIPPING MEANS FOR DEFLECTION RESPONSIVE TO PREDETERMINED CURRENT FLOW IN SAID CIRCUIT BREAKER; FIRST MEANS FOR MOUNTING SAID MAGNETIC TRIPPING MEANS, AND SECOND MEANS FOR MOUNTING SAID BIMETALLIC TRIPPING MEANS; SAID FIRST AND SECOND MEANS BEING SUBSTANTIALLY INDEPENDENT, WHEREBY A V-SHAPED AIR GAP RELATIONSHIP OF SAID ARMATURE AND PAIR OF POLE FACES IS MAINTAINED INDEPENDENT OF THE DEFLECTION OF SAID BIMETALLIC TRIPPING MEANS THERETO. 